Apparatus and method for carrying out diagnostic tests on batteries and for rapidly charging batteries

ABSTRACT

A method and system for performing automatic and rapid diagnostic testing and charging of a battery. The diagnostic test unit utilizes a charger combined with a rapidly variable load. After inputting battery characteristics including the cranking rating (CCA or CA) and the temperature of the battery, a diagnostic ramp procedure is utilized to provide an instantaneous current versus voltage analysis to determine the instantaneous cranking value (i.e., the single crank capability at full charge) of the battery being tested. If the instantaneous cranking value of the battery is above a level determined acceptable, a sustained discharge is carried out to tax the capacity of the battery. 
     At the end of the constant current discharge, the current is again to determine a loaded cranking value which simulates the battery power after multiple cranking attempts. If the loaded cranking value is below a desired percentage of the cranking rating, then the battery is put into charge. If a battery cannot be acceptably charged within the time of a given number of diagnostic probes, the battery is deemed to be a bad battery. The charging steps utilized during the diagnostic testing, as well as any charging of batteries determined to be good, utilizes a novel interactive stepping procedure which allows batteries determined to be good to be recharged in a minimum period of time without overheating the battery.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.60/094,308 filed on Jul. 27, 1998, now abandoned.

FIELD OF THE INVENTION

This invention relates generally to the field of lead-acid batteries,and, more particularly, to an apparatus and a method for rapidlycarrying out highly discriminating diagnostic tests on lead-acidbatteries and charging such batteries if appropriate.

BACKGROUND OF THE INVENTION

Over the years, the purchasing habits of customers for starting,lighting and ignition (“SLI”) batteries for automotive and otherapplications has changed. In the replacement market for SLI batteries,it has been increasingly the case that customers purchase such batteriesat mass merchandisers and that warranties, often relatively expensive,are provided.

Accordingly, when a customer has problems starting this vehicle andsuspects that the battery has gone bad, the customer returns the batteryto the retailer or other location where the battery was purchased, andthe warranty provided with the sale comes into play. A typicalresolution is that the retailer takes the “bad battery” back, providinga new battery.

Indeed, it seems that the battery gets the blame as the cause for theproblem regardless. Yet, it has been found that a significant proportionof batteries perceived as bad, and thus replaced per the warranty, arein fact lacking in charge, but capable of being recharged so as toprovide satisfactory performance in use. The warranty cost to both theretailer or other battery seller and to the battery manufacturer issubstantial.

For this reason, mass merchandisers and other battery sellers haveturned to various types of testing devices in an attempt to effectivelydistinguish between good and bad batteries. Some battery testers whichhave been used carry out simple fixed discharges to determine batterypower. Such testers are a variation of a standard load test in theindustry which discharges the battery at half its cold cranking rate for15 seconds and then looks for a minimum voltage adjusted for temperatureto determine whether the battery being tested is good or not. While sucha standard test is relatively simple and straightforward, this testrequires that the battery be highly charged, a condition usually lackingin batteries that are giving problems for whatever reason and are thusperceived as being bad. Such a standard test also requires a largesustained discharge current which, of course, discharges the batterysignificantly. Many commercial diagnostic testing units include a fixedresistor which discharges all batteries at a close-to-constant rate thatis well below the load test. Acceptable voltages are either fixed orrelative to the cranking rate of the battery.

Testing units can also combine charging with the discharge test.Charging usually is done with a straight fixed voltage or currentcharger from a simple transformer with a rectifying diode which tries toforce charge into the battery no matter what its condition. Yet,charging a battery can mask defects such as shorted cells and the like.Further, when batteries with shorted cells or bad internal connectionsare charged substantially, there can be a great deal of gassing andspewing of electrolyte which can be dangerous.

Another type of test unit proposed and used is a unit providing aconductance meter. Using relatively small current probes, the internalconductance of the battery is measured. This internal conductance isassumed to be proportional to the cranking rate of the battery,therefore providing a relative performance criteria. However, this typeof test unit does not stress or polarize the battery enough to determineif there is sufficient power to sustain a discharge for more than abrief instant and cannot accurately predict the full-charge performancewhen the battery being tested is in a heavily discharged condition. Suchan analysis also provides no information about the chargeability of thebattery being tested.

Accordingly, despite the clear need for a highly discriminatinglead-acid battery diagnostic test unit, it is believed that none of thetypes of test units being used satisfy the need. The warranty problem isa major issue in the lead-acid battery field which has simply not beensolved.

Indeed, the situation is perhaps exacerbated by the increasing role massmerchandisers play in selling SLI and other lead-acid batteries. Moreparticularly, the personnel responsible for dealing with battery returnsnot only do not have discriminating test units at their disposal, butare often less than adequately trained to deal with the many issuesunderlying whether a battery being returned is bad or good.

Still further, in many situations, the lack of patience of the customercan be evident. A decision as to whether the battery is good or badneeds to be capable of being provided in a relatively short period oftime. Additionally, if the battery is determined to be good but in adischarged condition, then the customer will want to have the batteryrecharged in as short a time as possible.

Given the many and varied parameters that need to be addressed to allowa highly discriminating diagnostic testing regiment to take place and torapidly recharge acceptable batteries, providing a suitable diagnostictest unit which can be safely used by the responsible personnel is aformidable task. Accordingly, it is a primary object of the presentinvention to provide a method and apparatus capable of rapidlydiscriminating between good and bad lead-acid batteries. A more specificobject of this invention provides a test regiment capable of carryingout the appropriate determination in no more than 15, and still morepreferably less than 10, minutes.

Another object lies in the provision of a diagnostic test unit capableof testing various types of lead-acid batteries having a variety ofcapacities as well as conditions while appropriately discriminatingbetween good and bad batteries.

Still another object of the present invention provides a diagnostic testunit which can be operated by personnel with limited training at most.

Yet another object of the present invention provides a diagnostic testunit characterized by safety features which minimize, if not eliminate,safety issues as regards both users and as to the test units themselves.

A more specific object of this invention lies in the provision of adiagnostic test unit which includes an interactive charging unit capableof rapidly and reliably recharging lead-acid batteries.

Other objects and advantages will become apparent from the followingdetailed description.

SUMMARY OF THE INVENTION

In general, the present invention provides a straightforward diagnostictest unit and system which automatically and rapidly takes advantage ofthe known phenomenon that battery resistance can be characterized bydischarging at various rates and measuring the resulting voltage. Thus,as is known, the current versus voltage relationship is linear and theproportionality constant is the resistance (or inversely theconductance) of the battery in a discharging mode. This can also providea derived voltage at vanishing current which represents the polarizedpotential of the battery. According to the present invention, thediagnostic test unit utilizes a charger combined with a rapidly variableload. Each is controlled by signals to and from a microprocessor; and,additionally, an input display provides directions to, and derivesinformation from, the system operator. After inputting the battery type(12V or 6V), the cold cranking rating (“CCA”) or cranking rating (“CA”),and providing the temperature of the battery, a diagnostic rampprocedure is utilized to provide an instantaneous current versus voltageanalysis to determine the instantaneous CCA (i.e., the single crankcapability at full charge) of the battery being tested. If theinstantaneous CCA of the battery being tested is above a leveldetermined acceptable, a sustained discharge is carried out to tax thecapacity of the battery.

The amount of time held at this sustained discharge rate is proportionalto the determined instantaneous CCA of the battery and the temperature.Small batteries with low CCA rates are discharged a shorter time thanlarge CCA batteries while cold batteries are discharged for a shorterperiod of time than are hot batteries.

At the end of the constant current discharge, the current is againramped from a high level to a lower level to determine a loaded orpolarized CCA which simulates the battery power after multiple crankingattempts. If the loaded CCA (i.e., the single crank capability at thepresent state of charge of the battery) is below a desired percentage ofthe rated capacity, then the battery is put into charge. It has beenfound that a battery does not have to be charged very much to respondacceptably to these ramping probes. Indeed, if a battery cannot beacceptably charged within the time of a given number of diagnosticprobes, the battery is deemed to be a bad battery.

In accordance with the preferred embodiment of the present invention,the charging steps utilized during the diagnostic testing, as well asany charging of batteries determined to be good, utilizes a novelinteractive stepping procedure which allows batteries determined to begood to be recharged in a minimum period of time without overheating thebattery or spewing electrolyte.

Additional features and advantages of the invention will be madeapparent from the following detailed description of illustrativeembodiments which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

While the appended claims set forth the features of the presentinvention with particularity, the invention, together with its objectsand advantages, may be best understood from the following detaileddescription taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a block diagram of a battery diagnostic tester and chargingsystem embodying the present invention;

FIG. 2 is a block diagram of a system controller for performingdiagnostic tests and charging a battery according to the invention;

FIG. 3 is a block diagram of DC sensors for sensing voltage and currentacross the battery terminals according to the invention;

FIG. 4 is a block diagram of a variable programmable DC powersupply/load for charging and discharging batteries according to theinvention;

FIG. 5 is a logic flow diagram illustrating the steps involved inperforming the diagnostic battery test and battery charge proceduresaccording to the present invention;

FIG. 6 is a logic flow diagram illustrating the steps involved instarting up the diagnostic tester and charging system;

FIGS. 7A and 7B are logic flow diagrams illustrating the steps involvedin performing the diagnostic procedure;

FIG. 8 is a logic flow diagram illustrating the steps involved inperforming the diagnostic ramp procedure;

FIG. 9A and 9B are logic flow diagrams illustrating the steps involvedin performing the charge start procedure;

FIG. 10 is a logic flow diagram illustrating the steps involved inperforming the charge control procedure;

FIG. 11 is a logic flow diagram illustrating the steps involved incharging the battery according to the interactive stepping procedure;

FIG. 12 is a logic flow diagram illustrating the steps involved inrunning the current stability reset procedure;

FIGS. 13A and 13B are logic flow diagrams illustrating the stepsinvolved in the check procedure;

FIGS. 14A and 14B are logic flow diagrams illustrating the stepsinvolved in conditioning or destratifying the cells of a battery;

FIG. 15 is a logic flow diagram illustrating the steps involved inmonitoring the current stability during the charging procedure;

FIG. 16 is a logic flow diagram illustrating the steps involved instopping the charger/discharger once a “good” battery is tested andcharged;

FIG. 17 is a logic flow diagram illustrating the steps involved once abattery is deemed untestable;

FIG. 18 is a logic flow diagram illustrating the steps involved inshutting down the charger/discharger if stopped by the operator or ifthe conducting cables are removed;

FIG. 19 is a logic flow diagram illustrating the steps involved inshutting off the charger/discharger if the battery tested is a failure;

FIG. 20 is a logic flow diagram illustrating the steps involved inshutting off the charger/discharger if a fault occurs;

FIGS. 21A and 21B are probing profiles that illustrate the steppedoutput voltage settings over time in conformance with the interactivestepping procedure; and

FIG. 22 is a graphical representation of the diagnostic tester andcharger unit according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a battery diagnostic testing systemand method that tests batteries under both charge and dischargeconditions yielding discriminating data relating to the condition andusability of the batteries. The invention is further directed to abattery charging system and method that rapidly recharges batteriesbased on an interactive charging procedure. While this invention isprimarily described with respect to the diagnostic testing and chargingof lead-acid batteries, there is no intention to limit the invention toany particular type of battery. Rather, the invention is specificallyintended to be used with all types of batteries capable of accepting anexternal charge, including, but not limited to, all types of lead-acidbatteries, nickel-cadmium batteries and other rechargeable batterytypes.

Turning to the drawings and referring first to FIG. 1, a diagnostictester and charging system 10 according to the invention comprises asystem controller 12, a variable programmable DC power supply and load14, DC sensors 24, conducting cables 18 and a battery 16. The systemcontroller 12 is coupled to the power supply 14 and includes controlcircuitry for regulating the output of the power supply 14. The powersupply and load 14 are coupled in a conventional manner to a battery 16using conducting cables 18 which link the power supply and load 14 tothe charging terminals 20, 22 of the battery 16. Depending on the amountof charge to be conveyed, the conducting cables 18 may compriseheavy-gauge copper wires or cabling compliant with National ElectricalCode requirements. The DC sensors, which sense current and voltageacross the battery terminals 20, 22, return the values thereof to thesystem controller 12 to which they are coupled.

As shown in FIG. 2, the system controller 12 comprises a microprocessor26, a memory 28, and input/output (I/O) circuitry 30 connected in aconventional manner. The memory 28 is comprised of random access memory(RAM), read-only memory (ROM) and the like. The I/O circuitry 30 iscoupled to an operator input 32 that comprises the means to inputrelevant operator commands and data, such as the rated CCA (ColdCranking Amps) of the battery. The I/O circuitry 30 is also coupled to adisplay 34 that comprises the means to display relevant output messages,such as messages informing the operator on the status of diagnostictesting or charging, or messages prompting the operator to entercommands or data. The I/O circuitry 30 is further coupled to the powersupply and load 14 and comprises the means to send commands originatingin the microprocessor 26 to the power supply and load 14 and to sendmessages originating in the power supply and load 14 to themicroprocessor 26. Similarly, the I/O circuitry 30, which is coupled tothe DC sensors 24 through the use of sensing leads, comprises the meansto receive sensor data.

The preferred system controller 12 includes analog-to-digital converters38 therein for converting the current and voltage measurements suppliedby the DC sensors 24 to digital values capable of being manipulated bythe microprocessor 26. The system controller 12 also includes adigital-to-analog converter 40 therein for converting a digital controlsignal to the proper analog signal required by the power supply and load14. In the preferred embodiment, pulse width modulators (PWMs) are usedin place of digital-to-analog converters 40 to generate the commandsignal. Moreover, in the preferred embodiment, the analog-to-digitalconverters 38 and pulse width modulators 40 are contained within, or onboard, the microprocessor 26 along with RAM and ROM 28. Alternatively,the analog-to-digital converters and pulse width modulators can beseparate devices contained within either the input/output circuitry 30(as shown) or the DC sensors 24.

One integrated circuit, a Microchip PIC17C756 microcontroller, has beenidentified as being particularly useful as a component within the systemcontroller 12, as it provides a microprocessor, RAM, ROM,analog-to-digital converters and timer/counter capabilities in a singlechip. The PIC17C756 analog-to-digital converters allow conversion of ananalog input signal, here voltage, to a corresponding 10-bit digitalnumber through the use of analog voltage comparators. The PIC17C756 alsoallows transmission of signals enabled through the use of on-board pulsewidth modulators.

As represented in FIG. 3, the exemplary diagnostic tester and charger iscomprised of four DC sensors: a charging current sensor 42, adischarging current sensor 44, a voltage sensor 46, and a reversepolarity sensor 48. As illustrated, the voltage sensor 46 is connectedin a conventional manner to measure the voltage across the terminals 20,22 of the battery 16. The voltage across the battery terminals is readand attenuated by a voltage attenuator in order to match the input rangeof the analog-to-digital converters 38 residing in the system controller12. The voltage sensor 46 is selected so as to be sensitive enough toreflect critical voltage changes with 0.01V accuracy.

The reverse polarity sensor 48, connected in a like manner across thebattery terminals 20, 22, senses negative voltage indicating that thebattery leads are connected backwards. The reverse polarity sensor 48 issimilarly connected to a voltage attenuator which scales the voltagereading to match the input range of the analog-to-digital converters 38.

The charging current sensor 42 and discharging current sensor 44 areconnected to measure the current across a shunt resistor 50. Due todifferences in current magnitude and sensitivity, two current sensorsmay be required to measure the charge and discharge currents. Thecharging current sensor 42, used to measure current flow into thebattery 16, is selected so as to be sensitive and accurate enough tomeasure changes in the charging current at the various steps of thecharging procedure. (See FIG. 11). According to the invention, thecharging current sensor 42 should be capable of sensing current in therange between 0 and 80 A.

The discharging sensor 44, used to measure current flow out of thebattery 16, is selected so as to be sensitive enough to measure a widerange of current during the diagnostic discharge routine. (See FIGS. 7Aand 7B). According to the invention, the discharge current sensor 44measures current flow between 0 and 400 A. In addition, the charging anddischarging current sensors are connected to a current amplifier whichscales the current reading to match the input range of theanalog-to-digital converters.

As shown in FIG. 4, the variable programmable DC power supply and load14 includes a DC power supply 52 and a variable load 54. According tothe invention, the power supply 14 is capable of providing an electricalcharge output at either a variable voltage level or a variable currentlevel (or both). The amount of current and/or voltage supplied by thepower supply 14 is determined by the system controller 12 which sendscommands to the power supply 14. The power supply 14, therefore,includes the means to interpret the commands which can be either in theform of digital signals or analog signals. In the preferred embodiment,pulse width modulators 50 are provided within the system controller 12so that the power supply only requires the means to interpret analogcommands.

To discharge current from the battery 16, a variable load 54 isprogrammed to provide a variable or constant (sustained) load between 0to 400 A. Programmable load variance is used to determine batteryperformance during diagnostic testing. The preferred variable load 54 iscomprised of a series of field effect transistors (FETs) connected toheat sinks. Alternatively, a series of straight resistors can be used tovary the load or one large resistor can be used while simultaneouslycharging and discharging to effectively vary the resistance or anycombinations thereof. Like the power supply 14, the variable load 54includes the means to interpret commands sent by the system controller12.

During the diagnostic test or charge, the system controller 12 maycontrol means 56 such as a relay, a switch or the like to automaticallyconnect the battery 16 to the circuit. For example, the switch 56 isopen while measuring the open circuit voltage of the system. Conversely,the switch 56 is closed allowing current to flow across a shunt resistor50 to enable charging, discharging and current measurements to be taken.

It can be readily appreciated that any number of equivalent systemcontrollers and DC power supplies/loads can be developed from otherdigital and analog circuitry components to perform the desired controlfunctions as described in more detail below. For example, a diagnostictester and charger apparatus has been implemented comprising an IBM486SX33 MHz personal computer as the system controller 12 executinginstructions originally written in the BASIC programming language (hereQuick Basic Version 4.5), to control a switch mode power supply and load14 via a data acquisition/control board interface bus. A diagnostictester and charger apparatus has also been implemented comprising asystem with an on-board microprocessor for measuring and adjusting thecomponents for charging and discharging but takes commands from a higherlevel processor on-board a PC computer via an RS232 interface bus.

While not necessary to the invention, it can also be readily appreciatedthat it is preferable to employ dedicated circuitry as the systemcontroller 12 and power supply and load 14 for use in commercialapplications such as in vehicle-based battery testing and chargingsystems or stand-alone battery testing and charging devices.

According to the invention, the system controller 12 executes a softwareroutine that performs diagnostic tests on a lead-acid battery todetermine whether the battery is “good” (e.g., capable of accepting acharge and delivering acceptable power). Upon determining that thebattery is good, the battery is charged to an appropriate level in atimely manner and may be conditioned to destratify the electrolyte andequalize the cells and electrodes. FIGS. 5-20 illustrate the stepsinvolved in performing the diagnostic battery test and charge methodaccording to the present invention.

FIG. 5 illustrates the overall procedure used to implement the currentinvention. The exemplary testing/charging procedure begins in step 100by connecting, in a conventional manner, the lead-acid battery to thediagnostic unit as illustrated in FIGS. 14-4. In step 102, the start upprocedure is invoked wherein proper connection of the battery to thediagnostic unit is verified, critical data is input by the operator viaappropriate buttons and keys, and the voltage is measured. At step 104,a preliminary determination is made as to whether the battery isuntestable by measuring a very low voltage after the start key ispressed. An untestable battery causes the procedure to stop at step 106and return to start at step 100. A testable battery proceeds to thediagnostic procedure at step 108 wherein the cold cranking amps, CCA, ofthe battery is measured through the use of current discharge. After thediagnostic procedure which is preceded by several charging attempts, thebattery being tested may be deemed “bad,” in which case at step 110 adecision is made to proceed to step 112 and end diagnostic testing andcharging on the battery. A “bad” battery is generally described as onewhich is either defective or appears to lack adequate cranking after oneor more charging attempts.

If the battery is not judged “bad,” however, at step 114 the chargerwill be turned on and the battery will be charged and checked inaccordance with the rapid interactive stepping procedure at step 116.During the charging process, in steps 118 through 130, a statusdetermination is repeatedly made as to the battery's viability. At step118, if the battery is judged “good and charged” to an acceptable level,the method proceeds to step 120 wherein the battery is eitherconditioned to destratify the electrolyte or the charge procedure isstopped. Alternatively, at step 122, if the battery is judged “bad,” themethod proceeds to the fail shutoff procedure at step 124 and thecharger/discharger is turned off. If, however, the operator pressed stopor the cables were removed during the charge procedure as determined instep 126, the method proceeds in step 128 to the shutdown procedure. Ifnone of the above conditions is fulfilled, meaning the battery has nottested good and is not adequately charged, the system proceeds to step130 where the system will either continue to charge the battery in step116 or retest the battery in step 108. In all, the system will attemptto charge and test the battery a limited set number of times beforedesignating the battery as bad and incapable of delivering adequatepower.

FIGS. 6 through 20 illustrate in more detail the various steps outlinedgenerally in FIG. 5. The start up procedure, illustrated in FIG. 6,begins at step 134 by resetting and calibrating the diagnostic testerunit. During this step, all critical variables are initialized asrequired by the method. For example, a variable AH, used to indicate thecapacity of a battery in ampere-hours, is zeroed. The reset step isimplemented at the beginning of each diagnostic testing/charging routinefor each battery regardless of whether the diagnostic unit is turned offbetween batteries. Upon completion of the reset and calibration step, atstep 136 a tester identification message is posted briefly on thedisplay and a small delay of two seconds is implemented to allow thesystem to stabilize. After the short delay, at step 138 the diagnostictester measures the battery open circuit voltage (OCV) with a switch 56such that the voltage sensor 46 and reverse polarity sensor 48 read thevoltage across the battery terminals 20, 22 without any load or charge.

In all, steps 138 through 150 determine whether the battery to be testedis properly connected to the diagnostic unit. For example, at step 140,the diagnostic unit determines if the operator has pressed the startbutton. If the start button has been pressed, at step 142, the OCV iscompared to an extremely low voltage to determine whether the battery istestable. If the battery's OCV is less than 0.3V, the method proceeds atstep 143 to run the untestable procedure which notifies the operatorthat the battery is untestable. (See FIG. 17). If the start button hasnot been pressed, at step 144, the OCV is compared to a low negativevoltage to determine whether the conducting cables 18 are properlyconnected to the battery 16. If the OCV is less than −0.5V, the methodproceeds at step 146 to notify the operator that the leads are reversed.If the OCV is greater than −0.5V, at step 148, the OCV is compared to anextremely low voltage to determine whether a battery is connected. Ifthe OCV is less than 0.3V, indicating that a battery is not connected,the method proceeds at step 150 to display a message instructing theoperator to connect the cables.

If the OCV is greater than 0.3V, indicating a properly connectedbattery, the method proceeds at step 151 to determine the type ofbattery that has been connected. If the OCV is less than 7.2V, at step152, the operator is prompted to enter the battery type. At step 153,the operator inputs the battery type, either 12V or 6V, depending on thetype connected to unit for testing. At step 154, the operator is nextprompted to enter the rating mode of the battery. As is known in theart, batteries are rated by the CCA (Cold Cranking Amps) or CA (CrankingAmps) of the battery, where CA is equal to approximately 1.2 times theCCA. The CCA of a battery is the number of amperes a lead-acid batteryat 0 degrees F (−17.8 degrees C.) can deliver for 30 seconds whilemaintaining at least 1.2 volts per cell (7.2 volts for a 12 voltbattery). A typical car battery will have a CCA in the range of 350 A to900 A. The CA of a battery is the number of amperes a lead-acid batteryat 32 degrees F. (0 degrees C.) can deliver for 30 seconds and maintainat least 1.2 volts per cell (7.2 volts for a 12 volt battery). Theoperator inputs the rating mode at step 155. The operator is nextprompted, at step 156, to input the battery's rated CCA or CA and atstep 157, the rated CCA or CA is input into the system. If the operatordoes not alter the default value of the battery rating, the CCAratedvariable is set to the previously tested value or the default value of550 A. In the case of a CA (cranking amps) rated battery, the defaultvalue is 650 A.

Next, at step 158, the method prompts the operator to input thebattery's temperature. As is known in the art, the temperature of thebattery is a major factor affecting the battery's cranking power.According to the invention, a temperature probe is used to accuratelymeasure the battery's temperature before the diagnostic test. Theexemplary diagnostic unit is equipped with an automatic temperatureprobe, such as an infrared temperature sensor or a thermocouple incontact with the battery. In the preferred embodiment, the temperaturesensor is in the form of a temperature gun pointed at the battery by theoperator. In another preferred embodiment, the temperature sensor is aninfrared sensor mounted in the diagnostic unit safety chamber havingsafety glass, as shown in FIG. 22, and may include a proximity sensorfor sensing the presence of the battery in the chamber. Alternatively, amanual device for measuring temperature such as a thermometer or thermalsensor strip affixed to the battery can be used. At step 159, thebattery temperature is input into the system. If the operator does notalter the battery temperature, the default value is set to 80° F. or theprevious temperature value.

Once critical battery information is input into the system, at step 160the operator is prompted to press start. The method then waits at step162 until start is pressed where upon the method proceeds to probe thebattery for a preliminary impression of chargeability. At step 164, thevoltage and current output in the power supply are set to appropriatelevels in order to create an inrush current. Thereafter, commands aresent to close the solenoid switch 56 to allow current flow into thebattery, to turn the charger on, and to set the start the system timer.

In steps 166 to 170, the start up routine loops until the inrush currentexceeds a nominal value, e.g., 4 A, at which point the diagnosticprocedure is invoked at step 170 (see FIGS. 7A and 7B). If, after anadequate time, e.g., fifteen seconds, the inrush current fails to exceeda low minimum threshold, around 0.5 A in the preferred embodiment, thebattery is deemed bad for failure to accept a charge and the start uproutine proceeds to the fail procedure at step 176. (See FIG. 19).

As illustrated in FIG. 7A, the exemplary diagnostic procedure begins instep 180 by informing the operator via the display 34 that testing hasbegun. In step 182, the method initializes the unit in preparation fordischarge testing. More specifically, the charger is turned off, atemperature factor used to accurately gauge the battery's CCA iscalculated, and all cranking variables critical to the procedure are setor reset. For example, the instantaneous CCA, CCAinst, which representsan estimate of the cold cranking power at full charge, is set to zero.In addition, the probe number counter is incremented to reflect thenumber of diagnostic attempts made at periodic intervals, e.g., fiveminutes, to test the battery. In the preferred embodiment, only alimited number of attempts, preferably four or less, are made to testany particular battery before the battery is deemed bad (see FIG. 9A,step 266). As a result, with the preferred five minute intervals ofcharge, diagnosis of the battery as “good” should occur within fifteenminutes or the battery is deemed “bad.”

After the probe number counter is incremented, the discharger is turnedon. Thereafter, in steps 184 through 196, the adjustable load isgradually increased from zero current in incremental amounts whicheffectively increases the discharge current flow from the battery. Inthe preferred embodiment, at step 184, the discharge current isincreased by 20 A during each pass until the load reaches 200 A. Aftereach increase in load, at step 186, the resultant voltage and currentare measured and the ampere-hours, AH, calculation is updated. In step188, the current output measured is compared to a minimum thresholdvalue. In the preferred embodiment, if the current output falls below 5A, the method proceeds at step 190 to the shutdown procedure. (See FIG.18). Similarly, in step 192, the voltage output measured is compared toa minimum threshold value. In the preferred embodiment, if the voltagedrops below a minimum of 7.2V, the discharge procedure is immediatelystopped at step 238 (FIG. 7B). Sustaining a high rate of discharge atlow voltages yields little information regarding the condition of thebattery and may lead to dangerous conditions. Before proceeding to thecharge routine, at step 194 the instantaneous CCA, CCAinst, iscalculated and at step 208 the CCA is set to zero. If voltage outputmeasures above a minimum threshold value, at step 196, the currentdischarge, Idischarge, is compared to a threshold discharge current.Once the threshold discharge current, set at 100 A in the preferredembodiment, is reached, the diagnostic ramp procedure is invoked at step198. (See FIG. 8).

The diagnostic ramp procedure, as illustrated in FIG. 8, begins at step244 by setting/resetting the ramping variables and setting the initialdischarge current, Idischarge, to a level of 100 A. Then in steps 245 to251, the discharge current level is incrementally increased to reach asafe upper ramp current. According to the invention, the battery shouldbe taxed at a reasonably high current value in order to producemeaningful values of battery resistance. In the preferred embodiment,the maximum discharge current should be near 400 A if the dischargevoltage is above a minimum level. During steps 245 to 251, the currentdischarge decrement, Y, is also determined so that the discharge rampprocedure cycles through a sufficient number of discharge steps in orderto produce an adequate number of data points for performing regressiontesting.

At step 252, the discharge current and voltage are measured across thebattery terminals and the ampere-hours, AH, calculation is updated. Asthe discharge process loops from step 252 to 262, the current is rapidlydecreased while the resultant current and voltage are measured at eachlevel until the load reaches a base level. According to the invention,the base level is equal to the high current value, A1, minus four timesthe current discharge decrement, Y. In the preferred embodiment, thebase level is near 200 A. At step 253, if the current drops below aminimum value, the method proceeds at step 254 to the shutdownprocedure. (See FIG. 18). In the preferred embodiment, a current readingbelow a minimum value of 5 A indicates cable removal or a connectioninterrupt.

Given an adequate current, however, at step 255 the current and voltagemeasurements taken at step 252 are stored in variable arrays and acounter, N, is incremented to track the number of iterativemeasurements. During the discharge procedure, the voltage and currentare examined to verify that the battery has adequate power. Low batterypower yields only meaningless battery measurements which are not helpfulin determining the battery's state as either good or bad. Therefore, atstep 256, if the voltage level drops below a minimum acceptable levelthe discharge procedure is stopped. In the preferred embodiment, a loadvoltage across the battery below 2V suspends the discharge routine untilthe battery is charged. If the discharge routine is suspended, a lowvalue estimate of the CCA of the battery is calculated at step 258 andthe process returns to the diagnostic procedure at step 268. Overall,the entire ramping discharge process generally lasts only a fraction ofa second and removes only a minimum amount of capacity from the battery.

Once the rapid discharge is complete and a base level is reached asindicated in step 262, the voltage and current data measured is used tocalculate regression parameters in step 264. For example, SA and SVrepresent the sum of all current and voltage measurements, respectively.Similarly, SA2 and SV2 represent the sum of all current and voltagemeasurements squared, respectively. Then, in step 266, the method usesthe regression parameters to determine the linear relation betweenvoltage and current wherein M represents the slope of the line in termsof negative ohms, R is the resistance in milliohms, and VACT is aresistance activation voltage. The resistance activation voltage iseasily determined to be the voltage at zero current predicted from thestraight current versus voltage line. A low VACT potentially indicates ashort in the battery or the battery is very discharged, whereas a highVACT means the battery is reasonably charged.

After completion of the first discharge routine, the diagnostic rampprocedure is exited at step 268 and the overall diagnostic procedureresumes processing at step 200 as illustrated in FIG. 7A. At step 200,the system determines whether a CCA has already been calculated bycomparing the CCA to zero. If a CCA has already been calculated, as instep 258 for the reason that the voltage dropped below a minimum setlevel, the process follows a separate path ultimately charging thebattery. Specifically, in step 202 the instantaneous CCA is set to thepreviously calculated CCA and the CCA is then set to zero in step 208.The system then proceeds, as shown in FIG. 7B, to turn off the dischargeunit in step 238 prior to attempting diagnostic testing again.

If the CCA is zero in step 200, indicating that the diagnostic rampproperly finished, at step 204 the system calculates the instantaneousCCA, CCAinst, based on previously calculated parameters. According tothe invention, CCAinst=((0.00618*BatteryTemperature+11.6)−(7.9+0.0043*Battery Temperature))*1000/R)/TemperatureFactor, where R is the resistance calculated during the diagnostic rampprocedure in step 198 and Temperature Factor is a value from 1 to 3stored in a lookup table. If the calculated instantaneous CCA is below afraction, k, of the rated CCA, as in step 206, no further dischargeoccurs. The method thereafter proceeds at step 208 to reset CCA to zeroand then at step 238 to turn off the discharge unit. The battery willthereafter be charged in an attempt increase its power. In the preferredembodiment, the tested battery should perform at or above sixty-fivepercent of the rated CCA in order to continue diagnostic testing. If theinstantaneous CCA is above the set level in step 206, a sustaineddischarge to tax the capacity of the battery is performed for a periodproportional to the determined instantaneous CCA of the battery at itspresent temperature. As such, batteries with a low CCA will bedischarged for a shorter period of time than those with a larger CCA.Similarly, cold batteries will be discharged for a shorter period oftime than hot batteries.

In the preferred embodiment, the constant current discharge is set to200 A, or half of the CCAinst if CCAinst is less than 400 A, and thetimer is started at step 210 in FIG. 7B. The procedure then loopsthrough steps 212 to 222, reading the resultant current, voltage andupdating the ampere-hours, AH, at step 212. In steps 214 and 218, thevoltage and current are compared to minimum threshold values during theconstant current discharge period. A current drop below 5 A indicates aconnection interrupt and the method proceeds to the shutdown procedurein step 216. (See FIG. 18). Similarly, if the voltage drops below 7.2V,the discharge routine is stopped and the battery proceeds to turn offthe discharge unit at step 238 after setting the CCA to zero at step200.

At the end of the constant current discharge as determined in step 222,the cranking variables are reset at step 224 and the diagnostic rampprocedure is invoked for the second time at step 226. As describedpreviously and illustrated in FIG. 8, the current is ramped from a highlevel to a lower level while recording the current and voltage readingsat each level. Upon returning from the diagnostic ramp procedure, atstep 228, a determination is made as to whether the CCA was calculated.If the CCA is not equal to zero, indicating the battery failed tocomplete the full ramp, a temperature adjustment is made at step 230 andthe discharge unit is turned off at step 238.

If the CCA is equal to zero, the second ramp data is then used todetermine a loaded or polarized CCA, at step 232, which represents thebattery's actual power after multiple cranking attempts. According tothe invention, CCA=((VACT−(7.9+0.0043*BatteryTemperature))*1000/R)/Temperature Factor, where VACT is the activationvoltage, R is the resistance calculated in step 266 of FIG. 8, andTemperature Factor is a value from 1 to 3 stored in a lookup table. Inaddition, 7.9 represents an adjustment factor required to predict coldcranking at 7.2V and 0.0043 represents the resultant change in voltagefrom a change in temperature. In addition to calculating the CCA in step232, the activation voltage, Vactl, is set to the resistance activationvoltage, VACT. At step 234, if the loaded or polarized CCA is below afraction, k, of the rated CCA, the discharge unit is turned off at step238. If, however, the loaded CCA is above a fraction of the rated CCA,the battery power is deemed acceptable or “good” at step 236. In thepreferred embodiment, the tested battery should perform at or abovesixty-five percent of the rated CCA in order to be deemed acceptable.Thereafter, the discharge unit is turned off at step 238 and the batteryproceeds to the charge routine in step 240.

The battery charging process begins with the charge start procedureillustrated in FIGS. 9A and 9B. Overall, the charge start procedureinitializes the system and prepares the battery to receive a charge.During the charging process precautions are taken to ensure the batteryis capable of accepting a charge as well as setting the charging valuesaccording to the specifics of the battery.

The charge start procedure begins at step 272 by performing an initialreading of the battery's current and voltage across the batteryterminals 20, 22 and starting a timer. Next, the system loops throughsteps 274 to 278 until the voltage across the terminals stabilizes or aset time elapses as indicated by the timer. In the preferred embodiment,at step 274, the most recent voltage reading is stored as Vk and newcurrent and voltage readings are measured at step 276 after a shortdelay, around 1 second. Then, at step 278 a comparison of the two mostrecent voltage readings, V and Vk, is made and fluctuations within theaccuracy range of the system, 0.01V, indicate the voltage is stabilizedallowing the method to proceed to step 280. For fluctuations greaterthan 0.01V, an elapsed time greater than twenty seconds also causes themethod to proceed to step 280.

At step 280, the open circuit voltage, Vopen, and shutoff voltage,Vshutoff, are set to the last voltage reading taken at step 276. If theopen circuit voltage is extremely low, less than 0.3V, as determined instep 282, the method proceeds to the fail routine at step 284. At thispoint in the charging process, an extremely low open circuit voltageindicates the battery has an extremely high resistance and is incapableof being charged or discharged, thus, requiring shut down of the chargeprocess. If an adequate open circuit voltage is measured, however, atstep 286, the method determines whether the battery previously tested“good” during the diagnostic routine. If the battery did not previouslytest good, at step 288, the method checks the probe number to identifythe number of times the charging routine has previously been initiated.If the probe counter is equal to one, indicating that the chargingroutine has not previously been initiated, the process cautiouslycontinues with the charge start procedure at step 302. If, however, theprobe counter is greater than one, indicating that the charging processwas previously run, six separate inquiries are made in series in steps290 to 300, to determine if the charging process should continue orproceed in step 301 to the fail routine as a result of a bad battery.

For example, in step 290, the method proceeds to the fail routine if theprobe counter reveals that charging has been attempted more than a setnumber of times. In the preferred embodiment, the system is limited tono more than four attempts at probing and three attempts at charging,lasting up to fifteen minutes. In step 292, the previous chargingcurrent, PREVAMP, is compared to an adequate charging current. If theprevious charging current is too low, less than 15 A, indicating thatthe battery is not charging at an acceptable rate, the method proceedsto the fail routine. In steps 294 to 298, other criteria are used todetermine if the battery should continue charging. If the battery failsany of these tests, the system will either proceed in step 301 to thefail routine as a result of a bad battery or proceed to step 300. Instep 300, a comparison of the calculated CCA and rated CCA is made sothat with each probe the acceptable performance, f(probe), graduallychanges thus taking into consideration numerous charging attempts whendetermining the state of the battery. If the battery does not pass thetest in step 300, the method proceeds to the fail procedure in step 301.

Referring back to step 286, if the battery previously tested “good”during the diagnostic routine or passed the tests in step 290 to 300,then the method proceeds to step 302 wherein the charge timer isstarted. Thereafter, in step 304, illustrated in FIG. 9B, all criticalcharging variables are reset. For example, the first and seconddifferential variables are reset to zero, all step current values arereset to zero, and the charger current setting is set to a nominalamount to allow the battery to accept an adequate charge.

At step 306, the charger voltage setting, Vset, is set to a voltagegreater than the previously measured open circuit voltage. In thepreferred embodiment, the charger voltage is set to 3.5V greater thanthe open circuit voltage if the battery was not previously determined tobe good, and 2V greater than the open circuit voltage if the battery waspreviously determined to be good. Also, at step 306, the maximumcharging current is set to the highest level acceptable, 70 A in thepreferred embodiment. However, at step 308, when the open circuitvoltage is then compared to a value empirically determined to be low fortypical batteries, if the open circuit voltage is below that value, lessthan 10.5V in the preferred embodiment, the system proceeds cautiouslyin the event the battery is shorted and at step 310 sets the chargervoltage and maximum charging current to values less than optimal.Thereafter, the charging current is set to the maximum charging currentand a charge setup timer is started at step 312.

In steps 314 through 320, a minimal delay is used to allow the voltageand current to stabilize. At step 314, voltage and current measurementsare taken and the battery's capacity in ampere-hours is updated. In step316, a current reading below a minimum threshold value, around 0.3 A,indicates a connection interrupt and the method proceeds to the shutdownprocedure at step 318. Otherwise, after a delay of thirty seconds atstep 320, the method proceeds to step 322.

In step 322, the charger voltage setting, Vset, is adjusted based on thestabilized voltage and current readings taken at step 314, the cableresistance and an anticipated rise in voltage. In addition, the chargercurrent setting, Iset, is increased by 5 A to allow latitude for currentexcursions in the stepping procedure. (See FIG. 11). Once the chargervoltage and current are properly set, the system proceeds to the chargecontrol procedure at step 324.

Overall, the charge control procedure, illustrated in FIG. 10, monitorsand controls the interactive charging of the battery such that thecharge process is maintained within certain effective and safeparameters. According to the invention, the procedure loops from step328 to 362 until either it is stopped by conditions placed in the loopwhich dictate the disposition of the battery, or the charge time exceedsthe maximum charge time allowed, or the capacity of the battery measuredin ampere-hours exceeds the maximum charging ampere-hours allowed.

Beginning with step 328, the average charging current is saved asPREVAMP for future comparisons. Next, in step 330 the current, voltageand time are read followed by an update of the average charging currentand battery capacity, AH, in step 332. Also, in step 332, the maximumcharging current is determined and an estimate of the remaining chargetime is calculated. Step 334 is a precautionary step which looks for asudden drop or low value in current, as in the case of removed cables ora faulty connection. In that situation, the potential for unsafeconditions due to arcing is high and therefore, the method proceeds instep 335 to the shutdown procedure in which the charger is immediatelyshut off. If the current is adequate, in step 336 the average chargingcurrent, Aave, is compared to the maximum measured charging currentMAXA. If the average charging current is greater than the previouslymeasured maximum charging current, then at step 337 the maximum measuredcharging current is reset.

In steps 338 to 348, the charge control procedure determines thecondition of the battery during the charging process. More particularly,in step 338, if the battery is deemed good and charged, the methodinforms the operator via the display 34 that the battery is good and itis acceptable to press stop in step 340. In step 342, if the battery isdeemed good, but not adequately charged, the method informs the operatorin step 344 that the battery is good and to wait for a complete charge.In step 346, if the battery is neither deemed good nor charged, themethod informs the operator in step 348 that the battery is charging andto wait for a diagnostic retest to determine the status of the battery.

In step 350, a comparison of the voltage measured at step 330 to themaximum allowable charging voltage, Vmax, is made. If the voltage is toohigh, the charger voltage setting is reduced minimally in step 356followed by a short time delay. Repeated small decrements of thecharging voltage will result in a drop in the current after a briefperiod of time. The method then bypasses the stepping procedure at step358 and proceeds to the check procedure at step 360. (See FIGS. 13A and13B). If the voltage in step 350 is not too high, then in step 352, acomparison of the average current as calculated in step 332 to the sumof the maximum charging current allowable and the absolute differentialcurrent of the first charging step, explained below, is made.

If the average current is greater than the sum, the method proceeds instep 354 to the current stability reset procedure. As illustrated inFIG. 12, the current stability reset procedure operates to reset variouscurrent stability factors when maximum current is achieved so that adetermination of current stability is bypassed. Beginning at step 434,the method first assures that the voltage is not falling at maximumcurrent. If the voltage is falling, the method proceeds at step 440 toreturn to the calling procedure. If the voltage is rising, at step 436the stability factors are reset to zero. At step 438, the shutoffvoltage comparator is saved for future use and at step 440, the methodreturns to the calling procedure. After completion of the currentstability reset procedure, the charger voltage setting is reduced with asmall time delay at step 356, the stepping procedure is bypassed and thecheck procedure is invoked at step 360. (See FIGS. 13A and 13B).

Referring back to step 352, if the average current is less than the sumof the maximum charging current allowable and the differential currentof the first charging step, the method proceeds to the steppingprocedure at step 358. According to the invention, once a battery isdeemed acceptable for charging, the system proceeds in a step-wisemanner to charge the battery as illustrated in FIG. 11. Overall,charging the battery is accomplished by first charging the battery at avoltage dependent on the base charging level, and then adjusting thebase charging voltage level in a direction that provides a more optimalcharge acceptance. The goal of charger method is to provide the maximumcharge while minimizing to the greatest extent possible gassing of thebattery. An exemplary step routine for charging a battery is disclosedin U.S. Pat. No. 5,589,757 assigned to the same assignee as that of thepresent application. The '757 method for step-charging batteriesdisclosed may be used in combination with the apparatus and methoddisclosed in the present invention.

In addition, a novel interactive stepping routine, illustrated in FIGS.11 and 21, may be used to adjust the charging output to the battery in adirection of a more optimal charge acceptance. Overall, the steppingprocedure requires that the charging output to the battery be adjustedso that the steps form two pairs of charging levels, where A1 and A2constitute one pair and A3 and A4 constitute a second pair. According toa primary aspect of the invention, three separate probing voltage stepsare coupled with a relaxation period to allow for the four separatecurrent measurements, A1, A2, A3, and A4.

As shown in FIG. 11, steps 368 to 396, and FIG. 21, a current A1 ismeasured after a short delay TD1. The voltage is then increased, stepone, and after a short delay TD2, the second current A2 is measured. Thevoltage output is then held constant for a relaxation period, TD3, toallow the current to stabilize. Thereafter, the third current, A3, ismeasured and the voltage is increased for a second time, step two.Finally, after a short delay, TD4, the current measurement, A4, is readand the voltage level is reset to its original amount. According to theinvention, step increases or decreases in voltage are chosen to gatherinformation about the battery during the charging process. In thepreferred embodiment, the step one and step two voltage changes are setto the same value, +/−0.0425V, and the reset voltage change is set totwo times the step one/step two voltage change (i.e., +/−0.085V) for 12Vbatteries. For 6V batteries, the step one/step two voltage changes arepreferably +/−0.02125V and the reset voltage change is +/−0.0425. Inaddition, time delays TD1, TD2, TD3, and TD4 are set to 250 ms, 150 ms,300 ms, and 125 ms respectively.

Once the four probing currents are measured, in step 398, threedifferential calculations are made. First, a lower differential, DA1,using the first pair of charging levels, A2 and A1, is calculated whereDA1 is equal to A2 minus A1. Similarly, an upper differential, DA2, iscalculated where DA2 is equal to A4 minus A3. Lastly, a seconddifferential, D2A, using the first differentials, DA1 and DA2, iscalculated where D2A is equal to DA1 minus DA2. Overall, the seconddifferential current, D2A, is used to adjust the charging voltagedirection. The D2A differences in current are accumulated in a movingaverage so that spurious individual readings do not dominate the system.Furthermore, the average is made relative on a zero to one scale andmultiplied by the voltage step increment to adjust the battery voltage.Ideally, the system adjusts the charging voltage until little or novoltage change is required to maintain an optimal charging level.

At step 400, the differential values are first evaluated to determine ifthe calculations yielded values within a normal range expected. If thevalues prove to be too large, the method skips ahead to step 414 usingpreviously calculated differential values. If the values are within anormal range, steps 402 to 410 limit the range and direction of thestepping voltage adjustment referred to as the “stepfraction.” In thepreferred embodiment, changes in the current measured by the seconddifferential are limited to increments of 0.1 or −0.1 so that onlyfractional corrections are made. The fractional corrections representthe rate of adjustment and the speed at which changes are made to thevoltage in order to charge at an optimal rate. The determination toincrement or decrement the voltage is made in steps 402 to 408. That is,second differential values greater than 0.1 result in a 0.1 step changeat step 404. Second differential values less than −0.1 result in a −0.1step change at step 408. As a result, second differential values greaterthan or equal to −0.1 and less than or equal to 0.1 result in no changesto the D2A value previously calculated.

Thereafter in step 410, a weighted average is calculated to smooth thestep changes and the stepfraction is normalized between zero and one. Astepfraction or change in voltage of one means a high rate of change isrequired, whereas a stepfraction of zero represents a zero rate ofadjustment indicating that the battery is being charged at an optimalrate. Prior to adjusting the charger voltage setting, a comparison ofseveral charging currents is made in step 412 in order to determine ifany further current adjustments are required to maintain current levelsat a maximum without large fluctuation. Specifically, the absolute valueof the difference between the average charging current and maximumcharging current allowed is compared to the absolute value of the firstdifferential, DA1. If the current is below the maximum level, at step414 a determination is made whether to increment or decrement thecharger voltage setting, Vset, by a factor of the stepfraction in steps416 and 418. However, if the current is at or near the maximum, at step420 the current stability reset procedure is invoked, as describedabove, to prevent shutdown at the maximum flat current. Then, at step422 the stepfraction is interpolated so that a change in the chargervoltage setting results in the maximum current for stability. At step424, a determination is made whether the average charging current isgreater than the maximum charging current. If greater, the chargervoltage setting, Vset, is reduced in step 418 and if less, the voltageis increased in step 426. After a current and time reading, an AHupdate, and a final time delay, TD5, at step 428, the system returns tothe charge control procedure at step 430. In the preferred embodiment,time delay TD5 is set to 200 ms.

Referring back to step 358 in FIG. 10, after completion of the steppingprocedure the check procedure is invoked at step 360. Overall, the checkprocedure, illustrated in FIGS. 13A and 13B, is used to determine when abattery is charged or in need of a retest, or to identify defectivebatteries. The check procedure begins at step 444 by first determiningwhether to measure current stability. A check of the charging stabilityis made periodically in order to ensure an abnormal current rise is notoccurring. In the preferred embodiment, a timer is used to enable acurrent stability check every two minutes.

If the timer does not indicate a stability check is necessary, themethod proceeds at step 460 to determine if the average chargingcurrent, Aave, is below a rate sufficient to condition and charge thebattery. If the average charging current is below the threshold level, afinal check of the battery's status is evaluated in steps 450 through458. At step 450, batteries which are “not good,” that is, shorted orlow powered, are identified. If the battery is non-responsive asindicated by various voltage readings so as to be considered not good,the system proceeds to the fail procedure in step 452. (See FIG. 19). Ifthe battery is responsive and behaving normally, at step 454 adetermination is made as to whether the battery requires conditioning.If the battery is sulfated or requires conditioning or destratification,the method proceeds to the conditioning procedure at step 456. (SeeFIGS. 14A and 14B). If conditioning is not required, the method proceedsat step 458 to the good/stop procedure. (See FIG. 16).

Referring back to step 460, if the average charging current is notsufficiently high, a check of the time is made at step 461 to verify adelay of 90 seconds. If the time delay is less than 90 seconds, thesystem proceeds to step 466 in FIG. 13B (see below). If a delay of 90seconds has elapsed, at step 462 various voltage, current and timingvariables are evaluated to determine if the battery is defective (e.g.,either shorted or not charging adequately). If the battery is defective,at step 464 the fail procedure is invoked. Otherwise, at step 466 inFIG. 13B the method determines whether the battery has previously beendeemed charged. That is, whether the flag which signals the battery isadequately charged has been set to true in which case the method returnsat step 468 to the charge control procedure. If the flag has not beenset to true, at step 470 the method evaluates the condition of thebattery to determine if the battery is in fact adequately charged. Ifthe battery meets the test as illustrated in step 470, the charged flagis set to true at step 472.

Next, at step 474 the checking procedure determines whether the batteryhas previously been deemed “good.” If the battery is good as indicatedby a flag, the checking procedure returns to the charge controlprocedure in step 468. If the battery has not yet been deemed good, thechecking procedure at step 476 determines for the second time whetherthe battery is charged. This condition will arise only if the batterymet the test of step 470 and the charged flag was set to true in step472. In that case, at step 482 the checking procedure determines if anysignificant charge has been applied to the battery so as to justify aretest. In the preferred embodiment, if the amount of charge since theend of the last charge period is extremely low, less than 0.5 AH, thesystem proceeds to the fail routine at step 484. However, if the chargeincrease is above the minimum threshold, the system proceeds to thediagnostic procedure for a retest in step 486. After the diagnosticprocedure, another determination is made as to whether the chargedbattery is “good.” At this point, if the battery has not been deemedgood, the system proceeds to the fail procedure in step 484. If thebattery is good, the system proceeds to the charge procedure in step 492and thereafter returns to the charge control procedure in step 468 tocomplete the charging process.

Referring back to step 476, if the battery is neither good nor charged,at step 478 the method determines whether enough time has elapsed towarrant another diagnostic run at step 480 or whether the system shouldreturn to the charge control procedure at step 490. In the preferredembodiment, diagnostic probes are run every five minutes followed by thecharge procedure. Therefore, if five minutes have elapsed since the lastprobe, the diagnostic procedure is invoked at step 480. Otherwise, themethod returns to the charge control procedure at step 490.

Returning to step 444 in FIG. 13A, if the stability timer indicates acheck in current stability is required, the system proceeds at step 446to the current stability check procedure. Overall, the current stabilitycheck procedure, as illustrated in FIG. 15, evaluates the chargedcapacity of the battery on a periodic basis to monitor the averagecharging current of the battery. In the preferred embodiment, thecurrent stability procedure is invoked every two minutes duringcharging. Beginning at step 549, the stability timer is restarted. Atstep 550, if the starting ampere-hours value, AHold, is equal to zero,which indicates a first reading of AH, the system saves the current AHmeasurement at step 552 and returns to the check procedure at step 566.If AHold is not equal to zero, the previously calculated averagecharging current is saved as AMPold and a new average charging currentis calculated at step 554. In the preferred embodiment, this calculationoccurs every three minutes. Next, at step 556, if AMPold is equal tozero, which indicates a second reading is complete, the system similarlyreturns at step 566 to the check procedure. If AMPold is not equal tozero, the system proceeds at step 558 to calculate the differentialcurrent drop, DC. Thereafter, at step 560, the differential current, DC,is compared to the minimum allowed current drop, DELA, to determine ifthe differential current is falling normally. If the current is fallingproperly as determined in step 560, the current rising flag remains atits default setting of false. If the current is rising, the currentrising flag is set to true at step 564.

After the flag is set, at step 566 the method returns to the checkprocedure and resumes processing at step 448 in FIG. 13A. At step 448,if the current rising flag is false, indicating a normal current dropsuch that the current is falling a fraction of an ampere, the methodcontinues with the checking procedure at step 460. A current rising flagset to true, however, indicates a potential for thermal runaway andresults in a final check of the battery's disposition in steps 450through 458 as described above.

According to the invention, after completion of the check procedure, abattery which is good and charged may proceed to the conditionprocedure. In the preferred embodiment, the operator is given the choiceto either disconnect the battery once it is deemed good and charged orleave it attached for conditioning. If the battery is left unattended,however, the battery will automatically be conditioned by default.Overall, the conditioning procedure equalizes the cells and electrodeswithin the cells of the battery which may have unequal discharge levelsor uneven electrolyte concentrations due to stratification. Conditioningis recommended in order to increase performance and life expectancy ofthe battery.

As illustrated in FIG. 14A, the conditioning procedure begins at step496 by informing the operator via the display 34 that the battery isgood and giving the operator the option to stop the conditioningprocess. In steps 498 through 510, an evaluation of various previouslymeasured charging parameters determines the level at which to set themaximum charging current, Imax. At a minimum, the maximum chargingcurrent will be set to 2 A. Thereafter, in step 512, variousconditioning parameters are set at limiting levels and conditioning isbegun. For example, the charger current is set to the maximum chargingcurrent allowed, the charger voltage is set to the maximum chargingvoltage allowed, and a voltage comparator, V1, is initialized at zero.In addition, at step 512 a timer, TIMEVCHECK, used to track periodictests of voltage stability, is initiated at zero. According to theinvention, the goal of the conditioning process is to charge until thereis a stable voltage, that is, to bring the voltage comparator, V1, equalto the battery voltage, V, within the accuracy of the system.

After the conditioning parameters are set, current voltage and currentmeasurements are taken and the battery capacity, AH, is updated at step514. At step 516 in FIG. 14B, the average voltage during conditioning,Vave, is set to the previous voltage calculation, V, followed by anothervoltage and current measurement and AH update at step 518. At step 520,if the current measurement is very low, less than 0.3 A, indicating thatthe cables were removed, the conditioning procedure is stopped and themethod proceeds directly to the shutdown procedure at step 522. However,if the current is adequate, a new voltage, V, is then calculated at step524 based on the average voltage during conditioning, Vave, and the lastvoltage measurement, V. This averaging process smoothes the measurementsto ensure consistent values.

Next, according to the invention, evaluation of the conditioning processoccurs at fixed intervals. In the preferred embodiment, the voltagestability is evaluated every ten minutes as determined by the timer,TIMEVCHECK, at step 526. If the timer indicates that ten minutes haveelapsed, at step 532 the voltage at the beginning and ending timeperiods are compared. If the voltage is constant or decreasing overtime, that is, V1 is greater than or equal to V, the system proceeds tothe good/stop procedure at step 546 since the conditioning process iscomplete. If the voltage is rising, indicating charging is not complete,the timer is restarted and the comparison voltage, V1, is reset to V atstep 536.

Referring back to step 526, if less than ten minutes have elapsed, themethod looks for low voltage readings at steps 528 and 538. At step 528,a voltage less than 12.5V is indicative of a shorted battery and thus,the method proceeds to the fail procedure at step 530. At step 538, avoltage less than 13.4V requires that the charger current setting beincremented by 0.1 A, with an upper limit of 10 A, in order to raise thevoltage so that conditioning can effectively proceed.

Finally, at step 544 the battery's capacity, AH, is compared to themaximum charging AH allowed, AHmax. If the capacity is less than themaximum allowed, the system loops back to step 516. Once the capacityexceeds the maximum, the system proceeds at step 546 to the good/stopprocedure.

FIGS. 16 through 20 illustrate the steps taken to inform the operator asto the disposition of the battery as determined by the diagnostic testerand charger method. The figures further illustrate the types of messagesand prompting implemented during the various shut down and precautionaryroutines. The good/stop procedure, illustrated in FIG. 16, isimplemented at various points in the overall diagnostic testing andcharging procedure after the battery is fully charged and tests “good”(see FIG. 13, step 458). The good/stop procedure begins at step 570 byturning off the charge/discharge unit. Next, at step 572 the operator isinformed via the display device 34 that testing is complete followed bya computer generated tone at step 574. In the preferred embodiment, thetesting complete message is displayed on the first line of the displaydevice.

In steps 576 through 588, the method loops until the battery cables areremoved and the operator presses a key. More particularly, at step 576,after a short delay, 1 second, a message informing the operator that thebattery tested “good” is displayed followed by another 1 second delay.Then, a message displaying the determined cranking value is displayed,also followed by a 1 second delay. The voltage is then read at step 577and evaluated at step 578. If the voltage measured is greater than athreshold voltage, indicating that a battery is present, the operator isinstructed to remove the cables at step 582. In the preferredembodiment, a voltage greater than 2V is used as the threshold voltage.Alternatively, if the voltage is less than 2V, the operator isinstructed to “press any key” at step 586.

In the preferred embodiment, the remove cables message or the press anykey message is displayed on the second line of the display device suchthat the message alternates being displayed every half second with thegood battery message displayed in step 576. Therefore, until the cablesare removed and a key press is registered at step 588, the method loopsback to step 576 and continues to display the results of the previoustest. In the preferred embodiment, the operator will disconnect thecables from the battery and press a key to start a new test on adifferent battery. Thus, once a key is pressed, the method proceeds tothe start up procedure at step 590 in FIG. 6 to begin testing again.

The untestable procedure, illustrated in FIG. 17, occurs when the opencircuit voltage registers a very low voltage, less than 0.3V, and theoperator presses the start key. (See FIG. 6, step 143). The untestableprocedure begins at step 594 by confirming that the charge/dischargeunit is turned off. Next, at step 596 the operator is informed via thedisplay device 34 that the battery is untestable/bad. At step 598, theoperator is instructed to press any key. In the preferred embodiment,the untestable/bad message or the press any key message is displayeduntil a key press is registered at step 600. Once a key is pressed, thedisplay is erased and the method proceeds to the start up procedure atstep 602. (See FIG. 6).

The shutdown procedure, illustrated in FIG. 18, is interrupt driven sothat when the operator selects stop via the input device the diagnosticor charging process ceases and is shutdown properly. Similarly, if theconducting cables 18 are disconnected during the diagnostic or chargingprocedure, an interrupt is generated and the shutdown procedure isinvoked immediately to minimize arcing and prevent potential sparking ifthe cables are reconnected. The shutdown procedure begins at step 618 byshutting off the charge/discharge unit. At step 619, the systemdetermines under what condition the system was shut down. If theoperator pressed the stop button, at step 620 a message indicating thatdiagnostic testing and charging was stopped by the operator is displayedfollowed by a computer generated tone to alert the operator at step 622.If the shut down was initiated by the removal of the cables, at step 621a message indicating that that cables were removed is displayed followedby a computer generated tone at step 622. In the preferred embodiment,these messages are displayed on the first line of the display device.

Thereafter, in steps 624 through 640, the operator is informed as to thestatus of the battery. In the preferred embodiment, an evaluation of twoflags determines which message is displayed to the operator. After ashort delay of 1 second at step 624, the flag settings are evaluated. Ifthe good and charged flags are true, the operator is informed that thebattery is good at step 628 followed by a 1 second delay and a messagedisplaying the determined cranking value, CCA. If the good flag is true,but the charged flag is false, the operator is informed that the batteryis good but has a low charge at step 632 followed by a 1 second delayand a message displaying the determined cranking value, CCA. Finally, ifnone of the conditions are met, at step 638 the operator is informedthat the test is incomplete. In the preferred embodiment, the messagedescribing the battery's disposition is displayed on the second line ofthe display device. Posting of the proper message is followed by a shortdelay of 1 second at step 640.

Thereafter, at step 641, the voltage is measured and evaluated at step642. If the voltage measured is greater than a threshold voltage, theoperator is instructed to remove the cables at step 646 followedperiodically by a computer generated tone at step 648. In the preferredembodiment, a voltage greater than 2V is used as the threshold voltage.If the voltage is less than 2V, the operator is instructed to press anykey at step 650.

In the preferred embodiment, the remove cables message or the press anykey message is displayed on the second line of the display device suchthat the message alternates being displayed every half second with thebattery's disposition message displayed in step 628 or 632. Therefore,until a key press is registered at step 652, the method loops back tostep 624. Once a key is pressed, the display is erased and the methodproceeds to the start up procedure at step 654. (See FIG. 6).

The fail procedure, illustrated in FIG. 19, may be implemented atvarious points in the overall diagnostic testing and charging procedureafter the battery is deemed “bad,” that is, defective or lackingadequate cranking after one or more charging attempts (see FIG. 9A, step301). The fail procedure begins at step 658, by turning off thecharge/discharge unit. Next, at step 660 the operator is informed viathe display device 34 that the battery is “bad” followed by a computergenerated tone at step 662. In the preferred embodiment, the bad batterymessage is displayed on the first line of the display device.

Next, the fail procedure loops through a display process from step 664to step 676 waiting for the operator to remove the cables and press anykey. In step 664, a short delay, 1 second, is followed by a messageinforming the operator to replace or adjust the battery followed byanother 1 second delay. Then, a message displaying the determinedcranking value is displayed, also followed by a 1 second delay. In thepreferred embodiment, these messages are displayed on the second line ofthe display device. The voltage is then measured at step 665 andevaluated at step 666. If the voltage measured is greater than athreshold voltage, the operator is instructed to remove the cables atstep 670 followed periodically by a computer generated tone at step 672.In the preferred embodiment a voltage greater than 2 is used as thethreshold voltage. If the voltage is less than 2V, the operator isinstructed to press any key at step 674.

In the preferred embodiment, the remove cables message or the press anykey message is displayed on the second line of the display device suchthat the message alternates, being displayed every half second with thereplace/adjust battery message displayed in step 664. Therefore, until akey press is registered at step 676, the method loops back to step 664.Once a key is pressed, the display is erased and the method proceeds tothe start up procedure at step 678. (See FIG. 6).

Like the shutdown procedure, the fault shutdown procedure, illustratedin FIG. 20, is interrupt driven. That is, if a fault occurs in thediagnostic unit, the fault generates an interrupt. In particular, faultsare generated by overheating or component failure. The fault shutdownprocedure is invoked at the beginning of the discharge procedure if thecurrent falls below an acceptable minimum level indicating a faultycurrent while at the same time the battery voltage is acceptable. Thefault shutdown procedure is also invoked at the beginning of the chargeprocedure if the current falls below an acceptable minimum level whileat the same time the battery voltage is unacceptable. When a faultoccurs in the unit, the operator should analyze the fault and determinethe source of the problem before initiating a retest.

The fault shutdown procedure begins at step 682 by turning off thecharge/discharge unit. Next, at step 684 the operator is informed viathe display device 34 that a fault shutoff has occurred followed by acomputer generated tone at step 685. The fault shutdown procedure thendetermines if the diagnostic unit requires servicing in step 686 to step690 because of charge of discharge failure.

If servicing is not required, a short delay 1 second at step 691 isfollowed by a unit temperature reading at step 692. If the temperatureis deemed high at step 693, for safety purposes a voltage comparison atstep 694 determines whether the operator is prompted to “remove cables”or simply “wait for reset” of the unit. If, however, the unittemperature is not deemed high the method proceeds to the start upprocedure at step 701. (See FIG. 6).

As can be seen from the foregoing, a method and system have beenprovided for testing and charging a battery wherein the microprocessorbased diagnostic test unit utilizes a charger combined with a rapidlyvariable load to safely and efficiently test, charge and conditionbatteries of various sizes and types. The disclosed diagnostic unit iscapable of adequately stressing the battery to accurately determine ifthere is sufficient power to sustain a discharge for more than a briefinstant. The diagnostic unit is also capable of accurately predictingthe chargeability and full-charge performance of the battery in additionto providing safe, rapid and reliable recharge of the battery.

In view of the many possible embodiments to which the principles of thisinvention may be applied, it should be recognized that the embodimentdescribed herein with respect to the drawing figures is meant to beillustrative only and should not be taken as limiting the scope ofinvention. For example, those of skill in the art will recognize thatthe elements of the illustrated embodiment shown in software may beimplemented in hardware and vice versa or that the illustratedembodiment can be modified in arrangement and detail without departingfrom the spirit of the invention. Therefore, the invention as describedherein contemplates all such embodiments as may come within the scope ofthe following claims and equivalents thereof.

I claim:
 1. In a battery diagnostic system, a method for performing adiagnostic test on a battery to determine if the battery is in acondition acceptable for recharging the battery, the method comprising:automatically determining an instantaneous cranking value for thebattery; and if the instantaneous cranking value for the battery isdetermined to be above a predetermined level, automatically performingthe further steps of: performing a sustained discharge of the battery togenerally tax the capacity of the battery; determining a loaded crankingvalue for the battery that generally simulates battery power aftermultiple cranking attempts; and if the loaded cranking value for thebattery is above a desired percentage of a rated cranking value for thebattery, deeming the battery to be in good condition for charging. 2.The method as recited in claim 1, wherein the step of automaticallydetermining the instantaneous cranking value for the battery furthercomprises using a cold cranking rating and temperature of the battery inconnection with a diagnostic ramp procedure to perform an instantaneouscurrent versus voltage analysis on the battery.
 3. The method as recitedin claim 2, further comprising the step of accepting from a user inputdevice the cold cranking rating of the battery and the temperature ofthe battery.
 4. The method as recited in claim 2, further comprising thestep of accepting from a temperature sensor the temperature of thebattery.
 5. The method as recited in claim 1, wherein the step ofdetermining the loaded cranking value for the battery further comprisesthe step of ramping a current discharged from the battery from a firstlevel to a second, lower level.
 6. The method as recited in claim 1,wherein the step of determining the loaded cranking value for thebattery further comprises the step of ramping a current discharged fromthe battery from a first level to a second, higher level.
 7. The methodas recited in claim 1, wherein the step of performing a sustaineddischarge of the battery further comprises the step of selectivelyplacing an adjustable load in electrical connection with the battery. 8.The method as recited in claim 1, if the loaded cranking value is belowa desired percentage of a rated cranking value for the battery,repeating the diagnostic test over a predetermined number of iterations.9. The method as recited in claim 1, further comprising the step ofsensing if the battery is connected to the system, and in response to asensed connection, prompting a user for a characteristic of the battery,and using the characteristic in performing the step of automaticallydetermining the instantaneous cranking value for the battery.
 10. Themethod as recited in claim 1, further comprising the step of sensing theopen circuit voltage of the battery and, if the open circuit voltage isbelow a predetermined value, performing further diagnostic tests on thebattery.
 11. A readable-medium having processor executable instructionsfor use in performing a diagnostic test on a battery to determine if thebattery is in a condition acceptable for recharging the battery, theinstructions performing the steps comprising: automatically determiningan instantaneous cranking value for the battery; and if theinstantaneous cranking value for the battery is determined to be above apredetermined level, automatically performing the further steps of:performing a sustained discharge of the battery to generally tax thecapacity of the battery; determining a loaded cranking value for thebattery that generally simulates battery power after multiple crankingattempts; and if the loaded cranking value is above a desired percentageof a rated cranking value for the battery, deeming the battery to be ingood condition for charging.
 12. In a battery diagnostic and chargingsystem, a method for performing a diagnostic test on a battery todetermine if the battery is in a condition acceptable for recharging thebattery, the method comprising: automatically determining theinstantaneous cranking value for the battery; and if the instantaneouscranking value for the battery is determined to be above a predeterminedlevel, automatically performing the further steps of: performing asustained discharge of the battery to generally tax the capacity of thebattery; determining a characteristic of the battery under load; and ifthe determined battery characteristic is within a desired percentage ofa rated characteristic for the battery, recharging the battery.
 13. Themethod as recited in claim 12, wherein the characteristic of the batteryis a loaded cranking value for the battery that generally simulatesbattery power after multiple cranking attempts.
 14. The method asrecited in claim 13, wherein the step of determining comprisesdetermining if the loaded cranking value for the battery is above adesired percentage of a rated cranking value for the battery.
 15. In abattery diagnostic and charging system, a method for operating thesystem comprising: accepting from a user input device a characteristicof a battery; and in response to the input of the characteristic,automatically performing the further steps of: determining if thebattery is in a condition to be recharged; and if the battery is in acondition to be recharged, recharging the battery.
 16. The method asrecited in claim 15, wherein the characteristic is the cold crankingrating of the battery.
 17. The method as recited in claim 15, furthercomprising the step of conditioning the battery after the battery hasbeen generally recharged.
 18. A method for performing a diagnostic teston a battery, the method comprising: discharging the battery from afirst predetermined amperage down to a base level amperage to determinea single crank capability of the battery; discharging the battery from asecond predetermined amperage down to the base level amperage todetermine a multiple crank capability of the battery; and determining astate of the battery using the single crank capability and the multiplecrank capability.
 19. The method as recited in claim 18, wherein thesecond predetermined amperage is higher than the first predeterminedamperage.
 20. The method as recited in claim 18, wherein the step ofdetermining the state of the battery comprises deriving a resistanceactivation voltage for the battery using the single crank capability andmultiple crank capability.